Usually when you don't collect it, it's waiting for you at the postmaster.

if this happens just start another round and whether you lose or win you'll get the reward you should have previously gotten. If you can, don't wager anything and try to just let the timer run out if you end up in a solo lobby or a lobby too far in for help. What you shouldn't do is not help the lobby if they have a fighting chance with your help, just remember not to offer a mote that run so as to not override the previous reward causing an endless loop of not getting anything.